Resources for twins and parents of twins
Fraternal Twins

Fraternal twins are formed when two eggs are released in the same cycle and both are fertilized. They are no different than non-twin siblings, except that they are born at the same time instead of years apart. As a result, they can look the same or different and can be the same sex or different sexes.

The odds of having twins that are fraternal are approximately 1 in 37 or 2.7%. Note those statistics include twins that are the result of fertility drugs and in vitro fertilization. The chances of having fraternal twins without the use of fertility drugs or IVF are approximately 1 in 55 or 1.8%. This is based on a study done in the year 2000 that estimated that 67% of twins were conceived naturally.

Fraternal twins run in families, though only on the woman’s side. Genetics play a role in causing a woman to release more than one egg in a cycle.